1. Field of the Invention
The present invention relates to a transmitter applicable for touch sensitive panels, and more particularly, to a transmitter capable of transmitting a plurality of frequencies simultaneously.
2. Description of the Prior Art
Touch sensitive panels or screens are important human-machine interfaces, especially on consumer electronic products like portable phones, tablets, or Personal Digital Assistances (PDAs). Touch sensitive screens are one of the main input/output (I/O) devices. Since capacitive touch sensitive screens, especially projected capacitive types, are very sensitive to finger touches, it has become the main design choice for touch sensitive panels/screens on the market.
Touching the screen with the tip of a finger will inevitably block part of the screen, and the user cannot confirm the point that is being detected by the touch sensitive with his/her eyes. In addition, one cannot have as accurate control as using a pen (stylus) when using the finger tips to write. Therefore, in addition to using the finger tips to touch the screen, the user may also wish to use a stylus for input to the screen.
Generally speaking, the area of the touch sensitive screen touched by the tip of a stylus is much smaller than that touched by a fingertip. For a capacitive touch sensitive screen, it is a big challenge to detect the capacitive changes caused by the stylus. Especially in many professional graphics or typesetting application environments, a lot of functional buttons are added to the stylus. Under such situations, the touch sensitive screen not only needs to detect the minute tip of the stylus, but also needs to detect whether the buttons are being pressed.
In summary, there is a need for a technique that supports a stylus with multiple functional input interfaces to allow a touch sensitive screen to detect the stylus and at the same time detecting the statuses of the functional buttons on the stylus.
From the above it is clear that prior art still has shortcomings. In order to solve these problems, efforts have long been made in vain, while ordinary products and methods offering no appropriate structures and methods. Thus, there is a need in the industry for a novel technique that solves these problems.